Hi!  You're lucky enough to have stumbled onto this link.

Here's what you do:

1.  Uninstall previous virtualboxes

     sudo apt remove virtualbox-5.0

2.  Download one of the virtualbox 5.0s such as 5.0.38 from the virtualbox site.  The xenial will do.

3.  Now install it like this:

     sudo dpkg -i --ignore-depends=libvpx3 virtualbox-5.0_5.0.38-114632-Ubuntu-xenial_amd64.deb

4.  Make sure you have libvpx4 installed:

     sudo apt-get install libvpx4

5.  Now you need to link vpx4 to vpx3:

     cd /lib/x86_64-linux-gnu/
     ln -s libvpx.so.4.1.0 libvpx.so.3

That's it!
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